U.S. patent number 9,595,659 [Application Number 14/266,244] was granted by the patent office on 2017-03-14 for piezoelectric vibration device for mobile terminal.
The grantee listed for this patent is Jung-Hoon Kim. Invention is credited to Jung-Hoon Kim.
United States Patent |
9,595,659 |
Kim |
March 14, 2017 |
Piezoelectric vibration device for mobile terminal
Abstract
A piezoelectric vibration device for a mobile terminal is
disclosed. A bimorph piezoelectric vibrator includes a pair of
piezoelectric element layers connected to one of positive and
negative poles and a middle electrode plate interposed between the
piezoelectric element layers and connected to the other pole. The
piezoelectric vibrator generates vibration due to up/down bending
displacement by fixing both end portions thereof to an inner
surface of a casing of a mobile terminal. A voltage-boosting
transformer raises a power source voltage of a mobile terminal to a
driving voltage. A driving chip receives the raised driving voltage
from the voltage-boosting transformer and drives the piezoelectric
vibrator. Weights are attached to at least one of both sides of the
piezoelectric vibrator to amplify vibration. Insulation members are
provided at both end portions of the piezoelectric vibrator to
prevent electricity applied to the piezoelectric vibrator from
leaking to the casing.
Inventors: |
Kim; Jung-Hoon (Daegu,
KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
Kim; Jung-Hoon |
Daegu |
N/A |
KR |
|
|
Family
ID: |
54355853 |
Appl.
No.: |
14/266,244 |
Filed: |
April 30, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20150318462 A1 |
Nov 5, 2015 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
41/183 (20130101); H01L 41/0933 (20130101); H01L
41/193 (20130101); G08B 6/00 (20130101); G06F
3/016 (20130101); H04M 19/047 (20130101) |
Current International
Class: |
H01L
41/08 (20060101); H01L 41/193 (20060101); G06F
3/01 (20060101); G08B 6/00 (20060101); H01L
41/09 (20060101); H01L 41/18 (20060101); H04M
19/04 (20060101) |
Field of
Search: |
;310/330,332,348,311,329 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dougherty; Thomas
Assistant Examiner: Addison; Karen B
Attorney, Agent or Firm: Novick, Kim & Lee, PLLC Kim;
Jae Youn
Claims
What is claimed is:
1. A piezoelectric vibration device for a mobile terminal,
comprising: a bimorph piezoelectric vibrator including a pair of
piezoelectric element layers connected to one of positive and
negative poles and a middle electrode plate interposed between the
piezoelectric element layers and connected to the other pole, the
piezoelectric vibrator being configured to generate vibration due
to up/down bending displacement by fixing both end portions of the
piezoelectric vibrator to an inner surface of a casing of a mobile
terminal; a voltage-boosting transformer to raise a power source
voltage of a mobile terminal to a driving voltage of about 20 to
about 300V; a driving chip to receive the raised driving voltage
from the voltage-boosting transformer and drive the piezoelectric
vibrator by the raised driving voltage; weights attached to at
least one of both sides of the piezoelectric vibrator in order to
amplify vibration of the piezoelectric vibrator; and insulation
members to insulate both end portions of the piezoelectric vibrator
from the inner surface of the casing, thereby preventing
electricity applied to the piezoelectric vibrator from leaking to
the casing.
2. The piezoelectric vibration device according to claim 1, further
comprising: soundproof sheets interposed between both end portions
of the piezoelectric vibrator and the casing in order to restrict a
noise due to vibration of the piezoelectric element layers.
3. The piezoelectric vibration device according to claim 1, wherein
the weights are made of a tungsten material having a relatively
high specific gravity and totally weigh from about 0.5 to about 5
g.
4. The piezoelectric vibration device according to claim 1, further
comprising: a protective tape attached to another side, opposite to
the side to which the weights are attached, of the piezoelectric
vibrator in order to prevent cracking of the piezoelectric element
layers.
5. The piezoelectric vibration device according to claim 4, wherein
the protective tape is attached to both sides of the piezoelectric
vibrator without the weights.
6. The piezoelectric vibration device according to claim 1, wherein
the piezoelectric element layers are made of one selected from a
material group including PZT-Polyvinylidene Fluoride (PZT-PVDF),
PZT-Silicone Rubber, PZT-Epoxy, PZT-Foaming Polymer, PVDF,
P(VDF-TrFE), P(VDF-TeFE) and TGS.
7. The piezoelectric vibration device according to claim 1, further
comprising: brackets to fix both end portions of the piezoelectric
vibrator to the inner surface of the casing.
8. The piezoelectric vibration device according to claim 1, wherein
the insulation members are configured with one of a thermal
shrinkable tape, an insulation tape, a silicone tube and an
insulation structure.
9. The piezoelectric vibration device according to claim 1, wherein
the piezoelectric element layers are coated with one of soft epoxy
and soft urethane on a surface thereof, thereby restricting noise
occurrence due to vibration and providing an insulation effect.
10. The piezoelectric vibration device according to claim 1,
wherein the insulation members provided at both end portions of the
piezoelectric vibrator are directly attached to the casing using
one of an epoxy adhesive agent and an acrylic adhesive agent.
11. The piezoelectric vibration device according to claim 1,
further comprising: a vibration module case into which the
piezoelectric vibrator is inserted, wherein both end portions of
the vibration module case are closed by a sealing adhesive agent,
thereby preventing sound generated due to vibration from leaking
outside.
12. The piezoelectric vibration device according to claim 11,
wherein the vibration module case is formed with a plurality of
through-holes through which an acoustic wave generated with
vibration of the piezoelectric vibrator inserted into the vibration
module case is transmitted outside.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a vibration device, and more
particularly, to a vibration device for a mobile terminal, which
generates vibration using piezoelectric effect.
Description of the Related Art
Recently, as virtual reality technology is developed, users
increasingly desire more detailed and realistic information through
virtual reality. One of the technologies developed to satisfy
users' desires is haptic technology which transmits tactile sense
and force. Such haptic technology is not only used for notification
function using a vibration motor in a mobile phone, but also is
widely used in various fields such as medical simulators, game
devices or the like.
Specifically, a haptic device as well as a monitor and a speaker
will be installed to a computing apparatus as an essential output
device. This is because installing a haptic device to a portable
electronic apparatus provides advantages of high perception of
tactile stimuli and superior interoperability with IT
apparatuses.
A vibration motor of a mobile terminal, which is a concrete example
of a haptic technology applied to a portable electronic apparatus
such as a smartphone, may enable a user to vividly feel vibration
by adding vibration to a sound and an image output from a mobile
terminal.
In general, a conventional vibration motor employed to a mobile
terminal is a vibration generator using weight eccentricity, which
simply vibrates the whole mobile terminal. A vibration device using
an eccentric rotating mass (ERM), which is configured to vibrate by
rotational eccentricity of a motor, has a response speed of about
200 ms. However, this response speed is quite insufficient to
satisfy a user's demand for operational simultaneity.
Another example of a vibration motor employed to a mobile terminal
is disclosed in Korean Patent Registration No.10-0793682, "MICRO
LINEAR VIBRATION DEVICE" (cited reference 1). A linear vibration
motor described in the cited reference 1 is configured to vibrate
by vertical linear movement using a coil and a magnet, and has a
response speed of about 50 ms. This response speed is greater than
that of the ERM, however, it is still insufficient to satisfy a
user's demand for operational simultaneity and cannot transmit
slight vibration to a specific body part such as a fingertip.
In order to realize a haptic function optimized to a portable
electronic apparatus, various vibration patterns including strong
vibration, slight vibration and the like should be controlled to
have an extremely high response speed. However, a vibration device
configured with an ERM using rotational eccentricity or a linear
motor using vertical linear movement just provides simple
vibration.
Therefore, it is required to develop a vibration device for a
mobile terminal, which can be precisely controlled to have a high
response speed capable of satisfying diverse and complicated
functions and can transmit slight vibration to a local body part
such as a fingertip.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a
piezoelectric vibration device for a mobile terminal, which has a
high response speed and a thickness for minimizing an internal
space of a mobile terminal, and vibration magnitude and speed of
which can be precisely and independently controlled.
It is another object of the present invention to provide a
piezoelectric vibration device for a mobile terminal, the amount of
vibration of which can be over two times more than that of a
conventional vibration motor, and which can achieve multi position
vibration.
In accordance with the present invention, the above and other
objects can be accomplished by the provision of a piezoelectric
vibration device for a mobile terminal, comprising: a bimorph
piezoelectric vibrator including a pair of piezoelectric element
layers connected to one of positive and negative poles and a middle
electrode plate interposed between the piezoelectric element layers
and connected to the other pole, the piezoelectric vibrator being
configured to generate vibration due to up/down bending
displacement by fixing both end portions of the piezoelectric
vibrator to an inner surface of a casing of a mobile terminal; a
voltage-boosting transformer to raise a power source voltage of a
mobile terminal to a driving voltage of about 20 to about 300V; a
driving chip to receive the raised driving voltage from the
voltage-boosting transformer and drive the piezoelectric vibrator
by the raised driving voltage; weights attached to at least one of
both sides of the piezoelectric vibrator in order to amplify
vibration of the piezoelectric vibrator; and insulation members to
insulate both end portions of the piezoelectric vibrator from the
inner surface of the casing, thereby preventing electricity applied
to the piezoelectric vibrator from leaking to the casing.
As is apparent from the above description, since the vibration
device using the bimorph piezoelectric element is mounted in a
limited space of a mobile terminal and generates vibration using a
reverse piezoelectric effect, a response speed is increased so as
to generate a simultaneous vibration effect corresponding to sound
and image of a mobile terminal, and vibration magnitude and speed
can be precisely controlled.
Further, since the piezoelectric vibrator of the present invention
has a smaller thickness than a conventional vibration motor, the
space occupied by the vibrator is reduced, which is helpful to
manufacture slim mobile terminals. In addition, since a plurality
of vibrators can be mounted in a mobile terminal, various vibration
modes can be realized at the same time, the amount of vibration is
increased so as to enable a user to easily discriminate vibration
signals, and multi position vibration can be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and other advantages of the
present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
FIG. 1 is a conceptual view illustrating an operational principle
of bimorph parallel type piezoelectric element layers of a
piezoelectric vibration device for a mobile terminal according to
an embodiment of the present invention;
FIGS. 2a and 2b are views illustrating a vibration pattern of the
piezoelectric vibration device for a mobile terminal depicted in
FIG. 1;
FIG. 3 is a block diagram of the piezoelectric vibration device for
a mobile terminal according to the embodiment of the present
invention;
FIG. 4 is a perspective view illustrating constitution of
installing a piezoelectric vibrator to a case of a mobile
terminal;
FIGS. 5a and 5b are exploded perspective views of the piezoelectric
vibrator depicted in FIG. 4;
FIG. 6 is a perspective view illustrating a used state of the
piezoelectric vibration device for a mobile terminal according to
the embodiment of the present invention;
FIG. 7 is a sectional view of the piezoelectric vibration device
for a mobile terminal according to the embodiment of the present
invention;
FIG. 8 is a perspective view illustrating a used state of a
piezoelectric vibration device for a mobile terminal according to
another embodiment of the present invention;
FIGS. 9 and 10 are sectional views of the piezoelectric vibration
device for a mobile terminal according to another embodiment of the
present invention; and
FIGS. 11a through 11c are perspective views illustrating
constitution of installing a plurality of piezoelectric vibrators
to a case of a mobile terminal.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be
described in detail with reference to the annexed drawings.
A piezoelectric vibration device for a mobile terminal according to
an embodiment of the present invention is a vibration generator
using a piezoelectric effect.
A piezoelectric effect is defined as: a piezoelectric material
produces a voltage when subjected to mechanical strain. Conversely,
a reverse piezoelectric effect is defined as: a piezoelectric
material becomes mechanically strained when a high voltage is
applied to the same. The piezoelectric effect can be used in, for
example, a piezoelectric element for ignition (a lighter and a gas
stove), a pressure sensor, an accelerometer sensor and the like.
The reverse piezoelectric effect can be used in, for example, an
actuator, a piezo motor and the like.
Specifically, the vibration device of the present invention is
embodied with a vibration generator using the reverse piezoelectric
effect, wherein a piezoelectric element layer is made of a
piezoelectric material and vibration is generated using a property
that the piezoelectric material is mechanically strained by a
voltage applied thereto. The representative piezoelectric material
includes ferroelectric Lead Zirconate Titanate (PZT,
Pb(Ti,Zr)O.sub.3), Barium Titanate (BaTiO.sub.3) and the like, and
a piezoelectric ceramic is formed using the above.
Vibration devices using the piezoelectric effect may be classified
into a unimorph type, a bimorph type and a multimorph type. The
bimorph type may be classified into a serial type and a parallel
type according to a polarization direction.
The unimorph type is primarily used in acoustic wave generating
apparatuses such as a buzzer, an alarm, a speaker and the like. The
multimorph type is used to obtain a relatively large force while a
bending displacement of a piezoelectric element is small. Such a
unimorph type, bimorph type or multimorph type piezoelectric
element needs a voltage higher than a voltage used in a portable
electronic apparatus in order to produce vibration. Moreover,
because the multimorph type piezoelectric element includes four or
more layers, a thickness thereof becomes large and accordingly, it
is inappropriate to install the same to a mobile terminal such as a
smartphone which has a limited installation space therein.
The bimorph type piezoelectric element has an advantage in
generating vibration because the same can be operated by a
relatively low driving voltage, a resonant frequency band is
relatively low and a bending displacement generated by a voltage
applied thereto is relatively large.
In installing a vibration device using a reverse piezoelectric
effect to a mobile terminal, such as a smartphone, many
preconditions and restrictions in accordance with a slim design
trend of mobile terminals should be solved.
Preconditions and restrictions in realizing a vibration device for
a mobile terminal are as follows: a battery voltage of a portable
electronic apparatus and a voltage required to drive a
piezoelectric element should be considered, and limitation in size
and thickness of a piezoelectric element to be installed in a
limited space of a portable electronic apparatus and durability and
shock resistance of a piezoelectric element should also be
considered. Further, a vibration device should have insulation
property to prevent leakage of a current flowing through a
piezoelectric element. In addition, a vibration device should have
vibration amplifying process and constitution to amplify vibration
of a piezoelectric element and transmit the amplified vibration to
a casing of a mobile terminal.
However, the present inventor has solved the above preconditions
and restrictions in realizing a vibration device using a reverse
piezoelectric effect by choosing a bimorph type piezoelectric
element based upon various experiments and studies.
FIG. 1 is a view schematically illustrating an operational
principle of a piezoelectric vibration device including bimorph
parallel type piezoelectric element layers according to an
embodiment of the present invention.
A piezoelectric vibrator 2 includes piezoelectric element layers 6
which have piezoelectric property and are arranged parallel to each
other and a middle electrode plate 4 interposed between the
piezoelectric element layers 6. One of positive and negative poles
is connected to the piezoelectric element layers 6, and the other
pole is connected to the middle electrode plate 4.
If a driving voltage for driving the piezoelectric vibrator 2 is
applied to the piezoelectric element layers 6 and the middle
electrode plate 4, positive charges and negative charges in the
piezoelectric elements layers 6 are aligned in a polarization
direction from an arbitrary arrangement state. If positive and
negative voltages are alternately applied to the middle electrode
plate 4 and the piezoelectric element layers 6 connected in
parallel as illustrated in FIG. 1, an expansion and contraction
phenomenon occurs.
One end or both ends of the piezoelectric vibrator 2 in FIG. 1 may
be fixed. As illustrated in FIG. 2a, in the case in which one end
of the piezoelectric vibrator 2 is fixed, the other end becomes a
free end which can be bent up and down. As illustrated in FIG. 2b,
in the case in which both ends are fixed, a center portion of the
piezoelectric vibrator 2 can be bent up and down (expansion and
contraction). Bending displacement caused by such repeated up and
down bending of the piezoelectric vibrator 2 generates
vibration.
Different from a conventional linear vibration motor in which
vibration is generated by resonance with a motor structure using a
fixed frequency (e.g., about 175 Hz), the vibration device using
piezoelectric features according to the present invention can
generate vibration by frequency variation within a wide frequency
band range from about 0 to about 300 Hz.
Further, the piezoelectric vibrator 2 has a response speed of about
0.002 second or less and can be precisely controlled in vibration
magnitude and speed by adjusting a frequency within a range from
about 0 to about 300 Hz, which generates a delicate and
simultaneous vibration effect corresponding to sound and image of a
mobile terminal.
A driving voltage for driving the piezoelectric vibrator 2 is
preferably in the range from about 20 to about 300V. A driving unit
15 includes a voltage-boosting transformer 18 to raise a power
source voltage of a mobile terminal to a driving voltage and a
driving chip 16 to drive the piezoelectric vibrator 2 by the raised
driving voltage. The raised driving voltage is applied to the
piezoelectric vibrator 2 through the driving unit 15.
If a voltage raised by the voltage-boosting transformer 18 and
applied to the piezoelectric vibrator 2 is less than about 20V, the
vibration device may not be operated. If a voltage is greater than
about 300V, an electric load may be too high to apply the voltage
to an electronic apparatus such as a mobile terminal.
In the embodiments of the present invention, vibration is generated
by periodically supplying and cutting off a voltage to the
piezoelectric vibrator 2 or alternately applying positive and
negative voltages to the piezoelectric vibrator 2. Preferably, the
middle electrode plate 4 of the piezoelectric vibrator 2 may be
made of a material having excellent electrical conductivity and
flexibility.
Because the piezoelectric vibrator 2 of the present invention is
attached to an electronic apparatus such as a smartphone, it is
desirable that the piezoelectric vibrator 2 has a small thickness
and the piezoelectric element layers 6 are made of a PZT
piezoelectric ceramic, however, the material of the piezoelectric
element layers 6 is not limited thereto.
If the piezoelectric element layers 6 are only made of a
polycrystalline ceramic material (hard PZT), the piezoelectric
element layers 6 may be easily cracked by vibration generated by
bending, shock by falling of a product or the like. Therefore, the
piezoelectric element layers 6 are made of one selected from a
composite material group including PZT-Polyvinylidene Fluoride
(PZT-PVDF), PZT-Silicone Rubber, PZT-Epoxy, PZT-Foaming Polymer and
the like or one selected from a polymeric material group including
PVDF, P(VDF-TrFE), P(VDF-TeFE), TGS and the like. Accordingly, the
piezoelectric element layers 6 can be prevented from being cracked
by enhancing durability while reducing a thickness.
More particularly, the piezoelectric vibrator 2 has preferably a
thickness of about 0.3 to about 1 mm so as to satisfy installation
conditions in accordance with a lightweight and slim design trend
of electronic apparatuses.
The piezoelectric vibration device for a mobile terminal according
to a preferred embodiment of the present invention will now be
described in detail with reference to FIGS. 4 through 7.
Referring to FIG. 4, the piezoelectric vibrator 2 of the present
invention includes the middle electrode plate 4 having high
electrical conductivity and the piezoelectric element layers 6 made
of a ceramic material and attached to both sides of the middle
electrode plate 4. After the piezoelectric vibrator 2 is formed by
integrally coupling the middle electrode plate 4 and the
piezoelectric element layers 6, electric power is periodically
supplied and cut off to the middle electrode plate 4 and the
piezoelectric element layers 6.
In this embodiment, a voltage is applied to the middle electrode
plate 4 and the piezoelectric element layers 6 in a flexible
printed circuit board (FPCB) form in order to minimize a whole
thickness of the piezoelectric vibrator 2.
Referring to FIG. 5a, the piezoelectric vibrator 2 further includes
a plurality of weights 8 which are attached to one side of one of
the piezoelectric element layers 6 in order to amplify vibration
generated by the voltage applied to the piezoelectric vibrator 2.
Although the piezoelectric vibrator 2 generates vibration by an
up/down bending displacement thereof, the vibration magnitude
transmitted to a mobile terminal is low. Such a problem can be
solved by the weights 8 which are uniformly formed and attached to
the piezoelectric element layer 6 so as to amplify vibration.
Preferably, the weights 8 attached to the piezoelectric vibrator 2
totally weigh from about 0.5 to about 5 g. If the weights 8 weigh
less than about 0.5 g, a vibration amplifying effect may not be
achieved sufficiently. Meanwhile, if the weights 8 weigh more than
about 5 g, a vibration amplifying effect may be achieved, however,
the piezoelectric vibrator 2 installed in a mobile terminal becomes
heavy and a response speed thereof becomes low. From such a point
of view, the lower limit value (i.e., 0.5 g) and the upper limit
value (i.e., 5 g) are set as critical values.
The weights 8 may be made of a tungsten material which has a
relatively high specific gravity and may be formed in a foil shape.
The weights 8 may be attached to the piezoelectric element layer 6
using an adhesive agent. The adhesive agent for adhesion of the
weights 8 may be an epoxy or acrylic adhesive agent.
The weights 8 may be attached to one side of the piezoelectric
vibrator 2 as shown in FIG. 5a, or may be attached to both sides of
the piezoelectric vibrator 2 as needed. In the case in which the
weights 8 are only attached to one side of the piezoelectric
vibrator 2, a protective tape 20 is attached to the other side, to
which the weights 8 are not attached, of the piezoelectric vibrator
2. The protective tape 20 serves to prevent the piezoelectric
ceramic from being cracked by vibration of the piezoelectric
vibrator 2, falling of a mobile terminal or other shocks. In
addition, the protective tape 20 provides an insulation effect.
In the case wherein the piezoelectric vibrator 2 is directly
attached to a rear surface of an LCD of a mobile terminal, the
weights 20 may not be attached to the piezoelectric vibrator 2. In
such a case, the protective tape 20 is attached to both sides of
the piezoelectric vibrator 2 in order to prevent cracking of the
piezoelectric ceramic and enhance an insulation effect.
The shape and number of the weights 8 are not limited to the
constitution illustrated in the drawings, and it should be
understood that the weights 8 can be installed in various shapes
and numbers.
If vibration of the piezoelectric vibrator 2 is directly
transmitted to a casing 14 of a mobile terminal, an acoustic wave
is naturally generated due to frequency rise. In order to prevent
this phenomenon, soundproof sheets 10 are interposed between the
piezoelectric element layers 6 and insulation members 12 at both
end portions of the piezoelectric vibrator 2, thereby restricting a
noise which may occur with vibration of the piezoelectric element
layers 6.
Describing in more detail, if a frequency is raised for vibration
of the piezoelectric vibrator 2, an acoustic wave is generated and
a noise is transmitted outside. A magnitude of the acoustic wave is
increased as vibration magnitude and speed are increased. By
attaching the soundproof sheets 10 to both end portions of the
piezoelectric vibrator 2, an acoustic wave generated due to
frequency rise is absorbed and noise transmission is prevented.
The soundproof sheets 10 are preferably made of a soft rubber
material such as silicon. The soundproof sheets 10 may also be made
of a material having good elasticity, such as fabric tape, elastic
rubber, resin tape, elastic silicone tube or the like. In addition,
the surface of the piezoelectric element layers 6 may be coated
with soft epoxy, soft urethane or the like, thereby restricting
noise occurrence due to vibration and providing an insulation
effect.
In the case in which sound as well as vibration generated from the
piezoelectric vibrator 2 is intended to be utilized, the soundproof
sheets 10 may be removed from both end portions of the
piezoelectric vibrator 2 or may be replaced with a hard material,
thereby producing both vibration and sound from a mobile
terminal.
As described above, a power source voltage of a mobile terminal is
raised by the voltage-boosting transformer 18 and then applied to
the piezoelectric vibrator 2 through the driving chip 16 so as to
generate vibration. Because a current according to a DC voltage of
about 20 to about 300V flows on the surface of the piezoelectric
vibrator 2 during the vibration operation, a structure for
preventing the current from leaking to the casing 14 is needed.
Accordingly, insulation members 12 are attached to both end
portions of the piezoelectric vibrator 2, to which the soundproof
sheets 10 are attached, so as to prevent electricity of the
piezoelectric vibrator 2 from leaking to the casing 14.
In this embodiment, by virtue of the insulation members attached to
both end portions of the piezoelectric vibrator 2 and the
protective tape 20 attached to the surface of the piezoelectric
element layer 6, a current according to the raised voltage is
prevented from leaking to the casing 14. The insulation members 12
are preferably configured with a thermal shrinkable tape having
insulation property, or may also be configured with an insulation
tape, a silicone tube or a separate insulation structure.
After the insulation members 12 are attached to both end portions
of the piezoelectric vibrator 2, brackets 13 for fixing the
piezoelectric vibrator 2 are coupled to both end portions of the
piezoelectric vibrator 2. The brackets 13 serve to fix the
piezoelectric vibrator 2 to an inner surface 14a of the casing 14
and are preferably formed to have a size corresponding to the
insulation members 12. The brackets 13 are preferably made of a
material having a high intensity with a small thickness. In this
embodiment, the brackets 13 are made of stainless steel such as
SUS410, or may be made of steel having a high intensity or plastic
material.
The brackets 13 may be attached to the inner surface 14a of the
casing 14 to fix the piezoelectric vibrator 2 by welding or
adhesion according to a material of a mobile terminal. In order to
minimize a thickness of the vibration device, the piezoelectric
vibrator 2, to which the insulation members 12 are attached, may be
directly attached to the casing 14 without the brackets 13. In this
case, an epoxy or acrylic adhesive agent may be used to directly
attach the piezoelectric vibrator 2 to the casing 14.
As illustrated in FIG. 5b, instead of the brackets 13 coupled to
the upper surface of the piezoelectric vibrator 2 to fix the same,
another type of brackets 13a, into which both end portions of the
piezoelectric vibrator 2 are inserted, may be used. In the case of
using the brackets 13a, a bottom surface of the brackets 13a may be
attached to the inner surface 14a of the casing 14 using an
adhesive agent.
FIG. 6 is a view illustrating a used state of the piezoelectric
vibration device of the present invention. Referring to the
drawing, both end portions of the piezoelectric vibrator 2 are
fixed to the inner surface 14a of the casing 14 of a mobile
terminal by the brackets 13, to thereby prevent separation of the
piezoelectric vibrator 2 due to vibration.
The vibration device of the present invention, as shown in FIGS. 8
and 9, includes a vibration module case 22. After the piezoelectric
vibrator 2 is securely fitted in the vibration module case 22, the
vibration module case 22 is attached to the inner surface 14a of
the casing 14.
Describing in more detail, the piezoelectric vibrator 2 is inserted
into an inner space of the vibration module case 22 through one
side portion of the vibration module case 22. Preferably, the
vibration module case 22 has the inner space which is large enough
to accommodate the piezoelectric vibrator 2, and is longer than the
piezoelectric vibrator 2. The vibration module case 22 is
preferably made of aluminum, stainless steel, steel, synthetic
resin or the like.
After the piezoelectric vibrator 2 is inserted into the vibration
module case 22, both end portions of the vibration module case 22
are closed by a sealing adhesive agent 24. The sealing adhesive
agent 24 may be silicon, a UV adhesive agent, epoxy or the like. By
closing both end portions of the vibration module case 22, the
sealing adhesive agent 24 has a soundproof function capable of
preventing an acoustic wave generated by vibration of the
piezoelectric vibrator 2 from leaking outside. In addition, the
vibration module case 22 has a function of protecting the
piezoelectric vibrator 2 inserted thereinto.
In the case in which sound as well as vibration generated from the
piezoelectric vibrator 2 inserted into the vibration module case 22
is intended to be utilized, as shown in FIG. 10, a plurality of
through-holes 26 are formed at an upper surface of the vibration
module case 22, through which an acoustic wave generated with
vibration of the piezoelectric vibrator 2 is transmitted outside,
so that a mobile terminal can produce both vibration and sound.
After the piezoelectric vibrator 2 is inserted into the vibration
module case 22, a lower surface of the vibration module case 22 is
attached to the inner surface 14a of the casing 14. An adhesive
agent for fixing the vibration module case 22 is preferably a
double-sided tape, or may be an epoxy or acrylic adhesive agent or
the like.
Since the whole lower surface of the vibration module case 22, into
which the piezoelectric vibrator 2 is inserted, is fixed to the
casing 14, an adhesion area is increased and thus the vibration
module case 22 can be stably fixed. Accordingly, an effect of
transmitting vibration generated from the piezoelectric vibrator 2
to a mobile terminal through the casing 14 is enhanced. Further,
since the vibration module case 22 and the piezoelectric vibrator 2
are integrally provided by insertion, a manufacturing time taken to
fix the vibration device to a mobile terminal can be shortened.
According to features of a mobile terminal, as illustrated in FIGS.
11a through 11c, the piezoelectric vibrator 2 of the present
invention may be provided in plural numbers which are arranged in
various patterns (e.g., arrangement in series, parallel or circular
shape) in the limited space of a mobile terminal, thereby producing
various vibration effects.
The structure, in which the plural piezoelectric vibrators 2 are
arranged in series or parallel as shown in FIGS. 11a and 11b, has
an effect of generating a feel in which vibration flows in one
direction (e.g., from left to right or vice versa, from up to down
or vice versa). The structure, in which the plural piezoelectric
vibrators 2 are arranged in a circular shape as shown in FIG. 11c,
has an effect of generating a feel in which vibration flows in a
circle.
The plurality of piezoelectric vibrators 2 mounted in a mobile
terminal is independently controlled. By controlling vibration
magnitude, speed and position of each of the piezoelectric
vibrators 2, vibration signals can be easily discriminated, and
multi position vibration as well as simple vibration can be
achieved.
The present invention can be used to all kinds of haptic devices,
such as OA devices, medical devices, mobile communication devices
and the like.
Although the preferred embodiments of the present invention have
been disclosed for illustrative purposes, those skilled in the art
will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
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